Solid-state 1H→19F/19F→1H CP/MAS NMR study of poly(vinylidene fluoride)

Solid-state H-1 --> F-19 and F-19 --> H-1 cross-polarization magic angle spinning (CP/MAS) NMR spectra have been investigated for a semicrystalline fluoropolymer, namely poly(vinylidene fluoride) (PVDF). The H-1 --> F-19 CP/MAS spectra can be fitted by five Lorentzian functions, and the amorphous peaks were selectively observed by the DIVAM CP pulse sequences. Solid-state spin-lock experiments showed significant differences in T-1rho(F) and T-1rho(H) between the crystalline and amorphous domains, and the effective time constants, T-HF* and T-1rho'* which were estimated from the H-1 --> F-19 CP curves, also clarify the difference in the strengths of dipolar interactions. Heteronuclear dipolar oscillation behaviour is observed in both standard CP and H-1 --> F-19 inversion recovery CP (IRCP) experiments. The inverse F-19 --> H-1 CP-MAS and H-1 --> F-19 CP-drain MAS experiments gave complementary information to the standard H-1 --> F-19 CP/MAS spectra in a manner reported in our previous papers for other fluoropolymers. The value of N-F/N-H (where N is a spin density) estimated from the CP-drain curve is within experimental error equal to unity, which is consistent with the chemical structure. Copyright (C) 2001 John Wiley Sons, Ltd.